California Wool Growers Association -
E. coli risks associated with grazing sheep in vegetable stubble fields, orchards and vineyards
The California Wool Growers Association in collaboration with University of California, Davis is developing a multiyear study to provide scientific data to identify the management and risk factors associated with E. coli and the utilization of sheep grazing in the crop stubble fields of California.
Recent outbreaks of E. coli O157:H7 linked to California produce have dramatically elevated concern that ruminants such as sheep grazing of crop residues may elevate levels of this pathogen in the soil and in subsequent crops grown at the grazed location. This concern is now being extended to the use of sheep as a non-chemical method for controlling unwanted vegetation in
orchards and vineyards.
In order to assess the validity of these claims and to develop science-based recommendations regarding sheep grazing and produce food safety, we need to answer several key questions.
First, what is the prevalence of E. coli O157:H7 in the feces of California sheep that graze crop residue and orchard/vineyard floor vegetation.
Secondly, what is the range of concentration or intensity of these bacteria in excreted sheep fecal material.
Thirdly, does this prevalence or intensity of fecal shedding E. coliO157:H7 shift upward or downward as sheep are rotated through different crop systems.
Lastly, what is the rate of inactivation of E. coli O157:H7 once it is deposited onto the soil surface and subsequently exposed to solar radiation or tilled into the soil profile in preparation for the next crop